The invention provides a desulfurization control method and device. The method comprises the following steps of: in a process of carrying out coal desulfurization through a circulating fluidized bed boiler, determining a prediction curve of an SO2 discharge in a predetermined time period, wherein the prediction curve corresponds to a plurality of predicted values at a plurality of moment's in thepredetermined time period; and adjusting a limestone input of the circulating fluidized bed boiler according to the prediction curve. By adoption above technical scheme, the problem that the limestoneinputs cannot be timely and correctly adjusted when coal desulfurization is carried out by using circulating fluidized bed boilers in correlation technique is solved, the lag of adjusting the limestone inputs according to SO2 measured values at chimneys is avoided, and the limestone input can be properly controlled at each moment.